Enzymes in Diagnosis

Question 1

How are enzymes used as diagnostic markers?

Answer 1

Enzyme activities measured in a serum

Question 2

What may imply tissue damage?

Answer 2

• Reduced levels of enzymes
• Intracellular enzymes in serum
• Distribution of enzymes in different tissues

Question 3

Why is leakage of intracellular enzymes into the blood dangerous?

Answer 3

Time after injury is crucial since enzymes have a different half-life in the blood stream

Question 4

What is enzyme activity measured in?

Answer 4

Expressed in standard units so that values between clinical labs can be compared
- Standard measure = International Unit (UI)

Question 5

What is 1 UI?

Answer 5

The amount of activity that will convert 1 micromole of substrate per minute under standard defined conditions

Question 6

What does a spike in enzyme activity precede?

Answer 6

Any liver damage

Question 7

What is increase of bilirubin normally an indicator of?

Answer 7

Jaundice

Question 8

What do elevated GOT levels indicate?

Answer 8

Normal 6-48/L

Acute liver damage

Question 9

What can albumin levels indicate?

Answer 9

Normal: 3.5-5.3/dL

Indicates loss of liver secretory function

Question 10

What can GPT levels indicate?

Answer 10

Normal: 7 to 55 IU/L

More specific indicator of liver damage

Question 11

What can alkaline phosphatase (ALP) levels indicate?

Answer 11

Normal: 45-120 IU/L

Elevation indicates large bile duct obstruction

Question 12

What is prothrombin time (INR)?

Answer 12

Measure of a patient’s ability to clot blood

Question 13

What are the cardiac injury markers?

Answer 13

1. Creatine kinase
2. Myoglobin
3. Cardiac Troponin-I
4. Lactate dehydrogenase

Question 14

What does creatine kinase release indicate?

Answer 14

Release indicated muscle damage

 Creatine phosphate acts as a store of high energy phosphate groups in muscle
 Reverses reaction when needed to get a burst of ATP

Question 15

What 2 polypeptides does creatine kinase (CK) comprise?

Answer 15

M and B subunits

Question 16

What structure of CK is mainly found in skeletal muscle?

Answer 16

MM (increase with AMI but also with skeletal muscle injury)

Question 17

What structure of CK is mainly found in the myocardium?

Answer 17

MB

Question 18

What is paracetamol overdose treated with?

Answer 18

Treatment with N-acetylcyseine with methionine

Question 19

What are typical blood glucose levels?

Answer 19

0.8-1.0

Question 20

What is level is hypoglycaemia?

Answer 20

<0.5 mg/ml

Question 21

What level is hyperglycaemia?

Answer 21

> 1.8 mg/ml

Question 22

What enzyme is important in childhood leukaemia? Why?

Answer 22

• Tumour cells deficient in Asn synthetase, therefore Asn becomes essential
  Treatment
• Deliver asparaginase
• Breaks down asparagine into aspartate
• Makes plasma levels of asparagine lower, specifically affecting growth of tumour cells

Question 23

What enzyme is given during coronary thrombosis and why?

Answer 23

1. Serine protease actin on fibrin clots
2. Produced using recombinant DNA technology
3. Rapid application can significantly increase chances of surviving coronary thrombosis

Question 24

What is urease used to break down?

Answer 24

Urease is used to breakdown the urea that builds up in patients with compromised kidney function

Question 25

What is function of an enzyme assay?

Answer 25

o Measures the conversion of substrate to product (Either the rate of appearance of product or the rate of disappearance of substrate is measured)
o Under conditions of cofactors, pH & temperature at which enzyme is optically active

Question 26

Why is a high [S] used during enzyme assay?

Answer 26

So that initial reaction rate is proportional to enzyme concentration